Both ways of contacting PSA's are each better for a particular use. You have to decide which you should employ in whatever specific situation that arises.
For example;
If you're seeking to establish or re-establish contact with a PSA that has not been active for awhile, then you should send directly to their email address. The PSA would only see the messages in SFI if and when they logged into SFI but they're not doing currently it.
Conversely, you would likely want to use a power tool like the PSA mailer when you wanted to broadcast an inspirational message or some team specific news. Plus you also get some Vpoints for doing that very thing weekly).
Both ways of contacting PSA's are each better for a particular use. You have to decide which you should employ in whatever specific situation that arises.
For example;
If you're seeking to establish or re-establish contact with a PSA that has not been active for awhile, then you should send directly to their email address. The PSA would only see the messages in SFI if and when they logged into SFI but they're not doing currently it.